The present invention relates generally to steroid hormones, and more specifically relates to novel steroids which are useful as anti-estrogenic agents. The invention additionally relates to methods for treating various disorders using the novel compounds, particularly conditions or diseases that are estrogen-dependent, i.e., are estrogen-induced or estrogen-stimulated, and to pharmaceutical compositions containing one or more of the novel compounds.
Breast cancer is one of the most prevalent types of cancer, and epidemiological and clinical studies have shown that approximately one-third of breast tumors are estrogen-dependent. This means that estrogens are required for the growth of such breast tumors in both premenopausal and postmenopausal patients. In postmenopausal women, in whom breast cancer most commonly occurs, breast tumor concentrations of estrone and estradiol are considerably higher than blood estrogen levels. Although retention of estrogens in breast tumors by high-affinity binding proteins contributes to the level of estrogens in tumors, estrogen concentrations in the breast are higher than plasma levels in breast cancer patients regardless of whether their tumors are estrogen receptor-positive (ER+) or receptor-negative (ERxe2x88x92). In situ formation of estrogen from estrogen biosynthetic precursors within tumors is now known to make a major contribution to the estrogen content of breast tumors.
Numerous other estrogen-dependent conditions, disorders and diseases have been identified as well, including, but not limited to, ovarian, uterine and pancreatic cancers, galactorrhea, McCune-Albright syndrome, benign breast disease, and endometriosis.
Estrogenic effects are mediated by specific receptors located in the nucleus of estrogen-responsive cells. The receptor contains a hormone binding domain for binding estrogen, transcription activating domains, and a DNA binding domain. The binding of the receptor-hormone complex to estrogen response elements (ERE""s) in the DNA of target genes is necessary for regulating gene transcription.
Drugs that competitively block estrogen binding to its receptor, termed anti-estrogens, are capable of inhibiting the stimulatory effects of the hormone on cell proliferation and are therefore useful in the clinical treatment of breast cancer. Clinically, estrogen receptor-positive tumors respond with a higher frequency to anti-estrogens than do tumors lacking a significant level of receptors.
Anti-estrogenic drugs fall into two chemical classes: nonsteroidal and steroidal. The nonsteroidal anti-estrogen tamoxifen (Nolvadex(copyright)) has been used as an adjunctive treatment for breast cancer following chemotherapy or radiation therapy. However, tamoxifen itself exhibits estrogenic activity in reproductive tissue, resulting in an increased risk of endometrial cancer and possible recurrence of breast cancer after long-term therapy. Furthermore, tamoxifen behaves only as a partial agonist in the uterus.
To date, little work has been done in the development of selective competitive antagonists of estrogen. Several steroidal anti-estrogens have been synthesized which lack estrogenic activity. Included among these are ICI 164,384, ICI 182,780 and RU 58668. See, e.g.: Wakeling et al. J. Steroid Biochem. 11:645-653 (1988), which pertains to ICI 164,384; Wakeling et al., Cancer Res. 51:3867-3873 (1991), and Wakeling et al., J. Steroid Biochem. Molec. Biol. 37:771-774 (1990), which pertain to ICI 182,780; and Van de Velde et al., Ann. N. Y. Acad Sci. 164-175 (1995), Van de Velde et al., Pathol. Biol. 42:30 (1994), and Nique et al., Drugs Future 2Q:362-366 (1995), which relate to RU 58668. Unfortunately, these drugs are not orally active and must be administered in high doses intramuscularly. Furthermore, the manufacture of these drugs is laborious, requiring a complicated, 14-16 step synthesis with very low overall yields. Potent steroidal anti-estrogens that are orally active have not yet been developed or commercialized, although the nonsteroidal mixed agonist/antagonist xe2x80x9craloxifenexe2x80x9d is currently available.
Accordingly, the present invention is directed to novel steroidal agents that are extremely effective anti-estrogenic agents, i.e., are potent antagonists of estrogen in breast and/or uterine tissue. The invention thus represents a significant advance in the art, particularly in the treatment of breast cancer and other diseases and conditions that are potentiated by the presence of estrogens.
Significantly, a number of the compounds of the invention that are potent, orally active agents, display tissue-selective pharmacology. That is, the compounds are useful as tissue-selective estrogen agonists/antagonists, also termed xe2x80x9cSelective Estrogen Receptor Modulatorsxe2x80x9d or xe2x80x9cSERMs.xe2x80x9d SERMs produce beneficial estrogen-like effects in some respects, notably on bone and lipid metabolism, while nevertheless acting as estrogen antagonists in the breast and/or uterus. The SERM profile may be distinguished from that of a pure estrogen such as 17xcex2-estradiol, which behaves as an estrogen agonist in all tissues, and from that of a pure anti-estrogen, which exhibits an estrogen antagonist profile in all tissue types.
The following references pertain to one or more aspects of the invention and as such may be of background interest to those skilled in the art: U.S. Pat. No. 2,840,581 to Hogg et al., which describes estradiol derivatives substituted at the 17-position with xe2x95x90CHxe2x80x94CH2OH and having estradiol-like activity; U.S. Pat. No. 3,536,703 to Colton et al., which describes antimicrobial estradiol derivatives substituted at C-3 with methoxy, and at C-17 with various groups, including xe2x95x90Cxe2x80x94CH2xe2x88x92NR3+ (wherein R is hydrogen or lower alkyl or wherein two R groups form a cyclic structure); U.S. Pat. No. 3,716,530 to Krubiner et al., which describes steroids containing various substituents at the C-17 position, including an estradiol derivative substituted at C-17 with xe2x95x90CHxe2x80x94CH2X, wherein X is halogen (stated to be useful as an intermediate in the synthesis of progestational compounds and antifungal agents); Blickenstaff et al., Steroids 46 (4,5): 889-902 (1985), which relates to estradiol derivatives having substituents at the 16-position bound to the steroid nucleus through a double bond, synthesized as part of a search for novel anti-cancer agents; French Patent No. 1,453,210, which shows estradiol analogs substituted at the 17xcex2-position with xe2x80x94CH(CH3)""Oxe2x80x94(CH2)2NRxe2x80x2Rxe2x80x3, wherein Rxe2x80x2 and Rxe2x80x3 may be alkyl or aralkyl; French Special Patent for Medications No. M3031, which relates to the synthesis of 3-hydroxy-20xcex1-dimethylaminoethoxy-19-norpregna-1,3,5(10)-triene; and Qian et al., J Steroid Biochem. 29(6):657-664 (1988), which evaluates the correlation between substitution at the 17-position of estradiol and possible anti-estrogenic activity, and describes estradiol analogs substituted at the 17xcex2-position with xe2x80x94Oxe2x80x94(CH2)2xe2x80x94NR1R2, wherein R1 and R2 are methyl, ethyl, cyclopentyl, cyclohexyl, or tetrahydropyranyl (none of the compounds were found to have anti-estrogenic activity).
In addition, the following references discuss tissue-selective anti-estrogens, or SERMs, and as such may be of interest with respect to the present invention as well: Grese et al. (1998), xe2x80x9cSynthesis and Pharmacology of Conformationally Restricted Raloxifene Analogues: Highly Potent Selective Estrogen Receptor Modulators,xe2x80x9d J. Med. Chem. 41: 1272-1283; Bryant et al. (1998), xe2x80x9cSelective Estrogen Receptor Modulators: An Alternative to Hormone Replacement Therapy,xe2x80x9d J. Soc. for Exper. Biol. and Medicine, pp. 45-52; Ke et al. (1998), xe2x80x9cEffects of CP-336,156, a New, Nonsteroidal Estrogen Agonist/Antagonist, on Bone, Serum Cholesterol, Uterus and Body Composition in Rat Models,xe2x80x9d Endocrinology 13(4):2068-2076; and Kauffman et al. (1997), xe2x80x9cHypocholesterolemic Activity of Raloxifene (LY139481): Pharmacological Characterization as a Selective Estrogen Receptor Modulator,xe2x80x9d J. Pharmacol. Experimental Therap. 280(1): 146-153. Reference may also be had to U.S. Pat. Nos. 5,447,941 to Zuckerman, 5,510,370 to Hock, 5,552,416 to Keohane, 5,578,613 to Bryant et al., 5,578,614 to Bryant et al., 5,593,987 to Cullinan et al., 5,610,167 to Cullinan, 5,641,790 to Draper, 5,646,137 to Black et al., 5,663,184 to Bryant et al., and 5,719,165 to Dodge, each of which pertains to different uses of tissue-selective anti-estrogens, particularly raloxifene.
No art of which applicants are aware, however, describes compounds as provided herein. To the best of applicants"" knowledge, the compounds and methods of the invention are previously unknown and completely unsuggested by the art.
Accordingly, it is a primary object of the invention to address the above-mentioned need in the art by providing novel steroid compounds useful as anti-estrogenic agents.
It is another object of the invention to provide novel compounds that are anti-estrogenic and have reduced estrogenic activity as may be determined by the degree of inhibition and degree of stimulation, respectively, of estradiol-induced alkaline phosphatase activity in human Ishikawa cells.
It is an additional object of the invention to provide such compounds which have substantially no estrogenic activity as may be determined by the aforementioned test.
It is still another object of the invention to provide such compounds in the form of steroidal active agents having a 1,3,5-estratriene nucleus that are preferably xe2x80x9c17-desoxy.xe2x80x9d
It is yet another object of the invention to provide a method for treating an individual with a disorder that is estrogen-dependent, i.e., an estrogen-induced or estrogen-stimulated condition or disease, by administering to the individual a therapeutically effective amount of an anti-estrogenic compound as provided herein, or a pharmaceutically acceptable salt thereof.
It is a further object of the invention to provide a pharmaceutical composition for treating an individual with a disorder that is estrogen-dependent, the composition comprising a therapeutically effective amount of a novel compound as provided herein or a pharmaceutically acceptable salt or ester thereof
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.
In one embodiment, then, the invention relates to novel compounds having anti-estrogenic activity and reduced estrogenic activity as determined by the degree of inhibition and degree of stimulation, respectively, of estradiol-induced alkaline phosphatase activity in human Ishikawa cells. Preferred compounds of the invention have a 1,3,5-estratriene nucleus, and are substituted at either the C-17 position or the C-11 position with a molecular moiety which renders the compounds effective to competitively block the binding of estrogen to its receptor. Of these, the more preferred compounds are xe2x80x9c17-desoxy,xe2x80x9d i.e., there is no oxygen atom bound directly to the C-17 position. Such compounds are encompassed, for example, by the generic structures of Formula (I) and (III) herein.
The preferred anti-estrogenic compounds of the invention are exemplified by Formula (I), Formula (II) and Formula (III), as follows: 
In Formula (I),
R is selected from the group consisting of C and N, and, when R is C, is in either the E or Z configuration;
r1 and r2 are optional double bonds;
X is hydrocarbyl, generally including at least one oxygen atom, sulfur atom, and/or nitrogen atom in the form of an xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NHxe2x80x94 or xe2x80x94N(alkyl)-linkage, and optionally containing additional substituents and functional groups such as hydroxyl, oxo, alkoxy, amino, alkyl-substituted amino, halogeno, aryl, heteroaryl, heterocycloalkyl, or the like;
Xxe2x80x2 is hydrogen or hydrocarbyl, generally including at least one oxygen atom, sulfur atom, and/or nitrogen atom in the form of an xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NHxe2x80x94 or xe2x80x94N(alkyl)-linkage, and, as for X, optionally including additional substituents and functional groups, or
X and Xxe2x80x2 may be linked to form a heterocyclic ring, typically a six- to eight-membered heterocycloalkyl ring containing one to four, typically two to three heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur;
when r2 is present, R1 is CR11R12 wherein R11 and R12 are hydrogen or lower alkyl, and when r2 is not present, R1 is hydrogen, alkyl, or halogen;
R2 is selected from the group consisting of hydrogen, hydroxyl, alkyl, alkenyl, aryl, alkaryl, xe2x80x94ONO2, xe2x80x94OR13 and xe2x80x94SR13 wherein R13 is alkyl, acyl or aryl;
R3 is selected from the group consisting of hydrogen, hydroxyl, halogen, alkyl, alkenyl, aryl, alkaryl, cyano, xe2x80x94OR13 and xe2x80x94SR13 wherein R13 is as defined previously;
R4 is hydrogen or lower alkyl;
R5 is selected from the group consisting of hydrogen, lower alkoxy, halogen, cyano, xe2x80x94CH2CHxe2x95x90CH2, xe2x80x94CHO, xe2x80x94NR14R15 and xe2x80x94(CH2)NR14R15 wherein R14 and R15 may be the same or different and are either hydrogen or alkyl, or together form a five- or six-membered cycloalkyl group optionally containing an additional nitrogen heteroatom;
R6 is selected from the group consisting of hydrogen, alkyl, acyl, xe2x80x94C(O)-aryl, xe2x80x94C(O)-alkyl and xe2x80x94SO2NH2;
R7 is selected from the group consisting of hydrogen, halogen, xe2x80x94NO2, xe2x80x94CHO, xe2x80x94CH2CHxe2x95x90CH2, xe2x80x94NR16R17 and xe2x80x94CH2NR16R17 wherein R16 and R17 may the same or different and are hydrogen, alkyl or acetyl;
R8 is selected from the group consisting of hydrogen, hydroxyl, xe2x80x94OR18 and xe2x80x94SR18 wherein R18 is alkyl, acyl or aryl;
R9 is hydrogen or alkyl, with the proviso that when R is N, R9 is not present; and
R10 is methyl or ethyl.
In another embodiment, the invention relates to novel compounds having the structure of Formula (II) 
wherein:
r1, r2, R, R1, R3, R4, R5, R6, R7, R8, R9, R10, X and Xxe2x80x2 are as defined above; and
R19 and R20 are independently selected from the group consisting of hydrogen, hydroxyl, alky, alkenyl, alkynyl, alkoxy, and halogen, or R19 and R20 together form xe2x95x90O.
In a further embodiment, the invention relates to novel compounds having the structure of Formula (III) 
wherein:
r2, R1 through R8 and R10 are as defined above;
m is an integer in the range of 0 to 6 inclusive;
n is 0 or 1;
R21 is hydrocarbyl including at least one oxygen atom, sulfur atom, and/or nitrogen atom in the form of an xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NHxe2x80x94 or xe2x80x94N(alkyl)xe2x80x94 linkage, and optionally including additional substituents and functional groups such as hydroxyl, oxo, alkoxy, amino, alkyl-substituted amino, halogeno, aryl, heteroaryl, heterocycloalkyl, or the like;
R22 is hydrogen or alkyl, or, when m is 0, R21 and R22 may be linked to form a five- or six-membered cyclic structure which may or may not be aromatic, containing 0 to 3 heteroatoms selected from the group consisting of N, O and S, and substituted with 0 to 4 substituents selected from the group consisting of alkyl, alkenyl, alkynyl, alkoxy, xe2x80x94C(O)-alkyl, xe2x80x94C(O)xe2x80x94O-alkyl, xe2x80x94Oxe2x80x94(CO)-alkyl, xe2x80x94C(O)-aryl, hydroxyl, carboxyl, halogen, nitrile, nitrate and fluorinated alkyl;
R23 is hydrogen or lower alkyl; and
R24 and R25 are both hydrogen or are both methylene bound to each other through a single covalent bond.
Each of Formula (I), (II) and (III) is intended to encompass pharmaceutically acceptable salts, esters, amides, prodrugs, and other analogs and derivatives of the compounds shown.
In another embodiment, the invention relates to pharmaceutical compositions containing, in combination, a pharmaceutically acceptable carrier and an anti-estrogenic compound of the invention, i.e., an agent that is anti-estrogenic but has reduced estrogenic activity as may be determined by the degree of inhibition and degree of stimulation, respectively, of estradiol-induced alkaline phosphatase activity in human Ishikawa cells. Preferred such compounds are steroids having a 1,3,5-estratriene nucleus that are 17-desoxy, and particularly preferred compounds have the side chain xe2x80x94(CH2)mxe2x80x94CHR21R22 at the 17-position, as shown in structural formula (III), with m, R21 and R22 as defined above. Typically, the pharmaceutical compositions containing as the active agent a compound defined by structural formula (I), (II) or (III).
In an additional embodiment, the invention relates to methods of using the novel compounds as anti-estrogenic agents. The novel anti-estrogenic compounds find utility in treating individuals with disorders that are estrogen-dependent, i.e., conditions or diseases that are estrogen-induced or estrogen-stimulated. Important examples of such a use include treatment of breast, uterine, ovarian and pancreatic cancers. The compounds may also be used in methods of treating certain conditions and disorders that are not estrogen-dependent, e.g., non-estrogen-dependent cancers, and particularly cancers which are multiple drug-resistant.
In a further embodiment, the invention relates to methods for using the compounds of the invention as tissue-selective anti-estrogenic agents, i.e., as xe2x80x9cSERMs,xe2x80x9d to treat or prevent breast disorders, to increase bone mass and/or inhibit bone loss, to lower serum cholesterol, and the like.